Chapter 9. Two-Wire Powered Sensors
The original LEGO MINDSTORMS brick, the RCX, used a two-wire powered sensor interface. The NXT has a backward compatibility mode with the old RCX sensors, and that mode offers some advantages for homebrew sensors that need higher voltages than the 4.3V supply described in Chapter 8. It's a natural choice for sensors that need to take full advantage of the 5V analog-to-digital conversion. Conveniently, the two wires are the same two wires you already used for passive sensors: the white and black wires in the NXT cable, or pins 1 and 2 on the port connector.
Signals
Power and sensor readings are combined on two wires by splitting the functions in time. First, the sensor signal is read, with exactly the same method ...
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